Smart move getting that backup ready! I learned that lesson the hard way last summer, mine died halfway through a fade. Now I keep two charged clippers minimum, plus I have their chargers always plugged in by the station. One backup can still fail or run out if you have a really long day, so a second one is cheap peace of mind. It totally kills your flow when you have to stop and scramble. How many charging spots do you have setup?
Get backups ready, like @jamie101 says. I run two charging stations with four ports total. That way, even if one clipper fails, I have fresh ones ready to go. It keeps the cuts smooth and the clients happy.
Yeah that's key.
Seriously, running out of battery mid-fade is the worst. It totally wrecks your rhythm. I was doing a really detailed beard line once and my main clipper just quit. Had to grab the backup, but it wasn't set to the same guard. Messed up the whole transition and I had to fix it. That's when I went and got a whole extra charging base too. Never letting that happen again.